Environment and development in coastal regions and in small islands

Monitoring the coastal zone of tropical southeast Africa for eco-tourism attributes and environmental influences on biodiversity

Introduction

3. Preliminary Results 

Zoological surveys 

There was an abundance of birds around the campsite during mornings and evenings, and their calls gave a positive attribute to the coastal forests. In the afternoon weather conditions (strong winds, high temperature) inhibited activity by insects and birds. A diversity of insects was found, including: butterflies, ants, beetles, dragonflies, scorpions, grasshoppers, bees, mosquitoes, moths, crickets and spiders. Earthworms were found mainly in the coastal forest and frogs in the grassland. Lizards were observed mainly in the coastal forest. Minimal evidence of mammal activity was found on the beach with more occurring in the coastal forest and grasslands. Numerous turtle tracks were noted along the beach. The species of birds identified from their calls and sight were:

Insects were collected from each trap and preserved in 70% alcohol for further identification at the University of Zululand. The results are listed below, and suggest a high biodiversity in the coastal forest (quadrats 2 and 3) and little overlap between quadrats. Hence the insects are habitat-specific.

Amphibians such as frogs were observed within the coastal forest and undisturbed grassland plot. The only reptiles identified were turtles, although crocodiles are often sited near the lake. There was evidence of nocturnal activity by small mammals on the beach from footprints found early in the morning.  A commonly occurring small mammal (pest) was the Vervet monkey found lingering around the campsite, snitching food from tourists. Hippopotami were observed in the lake from a distance, and local residents mentioned that crop production near the lake was often disrupted by hippopotami.

One grassland quadrat, originally thought to have been undisturbed, was seen to be grazed by cattle during the November 2000 survey and numerous new footpaths had been made by people involved in palm wine making and cattle tending. The lakeside plot was being used for farming purposes. Other activities included firewood collection, harvesting of mussels and fishing near the beach. Some tourists were involved in fishing and snorkeling. The survey team sampled pineapple and palm wine during their stay and visited a number of kraals to inspect the quality of life of the local community.   

Environmental survey results

Sea spray deposition results

The analysis of deposition indicates that the pH of the sea spray is relatively acidic. However the pH of the beach and foredune soils is more alkaline. It is not clear whether the methods employed are providing a consistent picture, so alternative approaches will be tested in follow-up activities. The sea spray will be further analysed for magnesium, sodium, calcium, potassium and nitrogen, to establish its nutrifying potential.

Soil samples were analysed for nitrogen, potassium, magnesium, calcium and phosphorous since they are essential minerals required for plant growth. Preliminary results are listed below. For nitrogen only one site (forest backdune) gave enhanced nutrient levels. Further work is necessary to obtain consistent results. At present it appears that the soils are poor everywhere - agricultural potential is limited.

Transect 1: soil analysis at 20 cm depth / 1 m depth

Transect 1: pH of soil at 20 cm depth

Transect 1: phosphorous levels in the soil at 20 cm depth

Transect 1: potassium levels in the soil at 20 cm depth

Transect 1: calcium levels in the soil at 20 cm depth

Transect 2 (north of Mabibi): soil analysis 20 cm depth / 1 m depth

Transect 2: magnesium levels in the soil at 20 cm depth

Physical and marine surveys

Beach sand profiles were taken with theodolite and staff at four locations and the slopes are analysed. Repeated measurements over a long period of time will enable a budget analysis of wind, surf and human influences on the flux of sand. 

Marine drifter tracks were analysed from double theodolite readings. Northward flow was observed on most days due to the southeasterly (oblique) swells. The strongest recorded drift was 1.0 m/s, whilst mean drift was ~ 0.4 m/s (20-30 m / min.). Directions were ~ 340°, eg. longshore to the north with a 15° shoreward component on most days. On two days strong northeast winds caused significantly weakened currents and a dominant onshore component of 290°. Residence times for marine organisms around the coral reefs would increase substantially then. As strong northeast winds (hence weak longshore currents) prevail about a third of the time, this finding is important for the management of coral reefs.

Launching the marine drifter in the surf zone off Mabibi

Humidity, temperature and wind speed and direction measurements were taken twice daily (10h00 and 16h00) at a number of positions inland along the transect. These were averaged for all days into morning and afternoon means to study contrasts induced by the land-sea interface and associated frictional effects. The humidity increases gradually toward the sea as expected, from a mean of < 60% to about 70% on the foredune and beach. Temperatures change in an opposing way, with cooler weather near the sea and warmer conditions leeward of the coastal dunes, in the grasslands. Slightly cooler weather is found near the lake. Surprisingly, the grassland temperatures were > 1° C higher at 10h00 than at 16h00. This appears to be due to the early sunrise (05h00) and light winds in the morning. Wind speeds were strong on the beach in the afternoons as expected (> 7 m/s), creating unpleasant conditions for eco-tourism (eg. blowing sand). Winds declined rapidly into the forest canopy (< 2 m/s) where frictional effects inhibit flow. Winds increased again in the grasslands, particularly in the afternoon. The coastal dune forests therefore act as a ‘sink’ for aeolian transported sediments, and gain some nutrients in the process. This may account for a portion of increased productivity there. Use by animals as a habitat also increases productivity of the coastal forests, and a budget analysis of these inputs is planned. The synergistic feedback between the integrity of the canopy and its productivity is a major ecological attribute. It is therefore recommended that the current management policy inhibiting access to, and resource extraction from, the coastal forests be maintained. The width of the coastal forest should be enhanced where possible, and our study needs to establish determinants of forest encroachment. 

Demographic surveys

Demographic results were generated by interviews within the community and with tourists on the beach. Many tourists prefer the natural setting of Mabibi and want the area to remain conserved. The local community needs jobs and development, so conflicting views are noted. The first phase of an on-going socio-economic survey was conducted on 30 households with a total of 314 people. The survey was intended to establish human activities, potential pathways to prosperity and environmental impacts. Of 189 adults surveyed, only 51 people are employed, mainly locally (59%). About one-third of households had no external source of formal income. All households engaged in subsistence agriculture –growing maize, peanuts, potatoes, etc. Another popular activity (67%) is the selling of goods, eg. grass mats, woodwork, etc. Harvesting marine resources (fish, mussels, etc.) is practiced by 53% of households. 

To place the demographic findings into an objective context, a ‘rural prosperity index’ is formulated with the elements:

 P = H + C + A 

• P is rural prosperity index

• H is health (determined via questionnaire and interviewer perceptions of happiness and physical appearance); 

• C is cash flow (established via questionnaire) from formal income or generated through extraction of local resources;

• A is cumulative assets (listed by the interviewer from inspection) including house and possessions. 

C creates quantifiable downstream ecological impacts in cases where, for example, slash and burn agriculture is employed to clear land for crops, or where fish, mussels or firewood are collected. The level of prosperity, averaged for households in Mabibi, is rather low. Demographic questionnaires revealed that insects such as bees are a useful food source for some members of the local community. They people had problems with grasshoppers, locusts and mosquitoes. A few isolated cases of malaria had been reported in the area recently. Tick-bite fever, however, is more widespread.

These results are in-progress and further work is needed to gain full insight to the cultural environment and social problems associated with limited opportunities for local employment. Given the poor soils, farming practices need to be limited to specialised crops such as cashews. Eco-tourism projects seem best placed to reap rewards.

Discussion

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